Performance studies of a separately excited DC motor speed control fed by a buck converter using optimized PIλDμ controller

In this paper, fractional order proportional integral derivative controller (FOPID) has been designed to get a desired performance form a separately excited Direct Current (DC) motor fed by a buck converter. The robustness of the DC motor speed control is increased using this FOPID controller due to the effect of increased iso-damping response. This increased iso-damping occurs due to the addition of two new variables i.e. integro-differential operators λ and μ in FOPID when compared with conventional PID controller. We have also discussed the rule of taking this integro-differential operator which can be used for further improvement of iso-damping response. The five variables (Kp, Ki, Kd, λ and μ) of the FOPID controller are optimized first considering frequency domain design criteria and secondly using time domain performance index. Mathematical model of the plant has been used in order to utilize the present scheme. Genetic Algorithm from MATLAB optimization toolbox has been used for solving the time and frequency based design criteria.